Status of alien species in the Mediterranean and Black Sea

54
Mediterranean coast. Schembri et al. (2010) reported that C. andromeda was observed off the Maltese
islands in the Central Mediterranean Sea.
4.3 Impacts on fisheries
Mostly in the eastern Mediterranean Sea, several alien species cause damages to fisheries. Caulerpa
taxifolia cause considerable fouling on fishing nets. Calinectes sapidus also damages nets with
entangling and cutting. In Turkey and Cyprus, fishers complain about L. scelaratus because they cut
hooks of longlines and bite off the captured fish in the nets or on the lines, which has a negative
economical impact on fishers of Israel and blocked gill-netting for several weeks (Spanier and Galil,
1991). Kideys and Gücü (1995) and Avşar (1999) reported that the proliferation of R. nomadica off
the eastern Mediterranean coast of Turkey has a potential risk to human health, tourism and fisheries.
In August 1995, many swimmers were stung and sought medical treatment. Local fishers claimed that
the catch from the gill net fisheries decreased and that the jellyfish entangled in their nets were a major
nuisance. In Iskenderun, due to mass jellyfish blooms, the fish farmers could not lift their nets to the
surface when they wanted to take the fish from the cages. R. nomadica do not move actively, thus
penetrates the Levant Sea like other lessepsian species’ spread pattern, following the Levantine current
system. Avşar (1999) also reported that firstly they reached Lebanon and Syrian Arab Republic, then
the Turkish eastern Mediterranean coasts, clinging to fishing nets and causing economic damages.
Impacts of the alien species should be considered also for the fisheries management, because the
traditional mesh size of the fishing nets may need to be changed due to new commercial species
mostly in the eastern Mediterranean countries. This involves extra costs for fishers or fishing
communities, which were difficult for traditional fishers who have limited financial source. Another
issue is that fish inspectors can easily confuse native and alien fishes when they examine control the
size limitation of the fish on the deck of fishing boats, e.g. native mullet Mullus barbatus, Mullus
surmelatus vs U. moluccensis. Some of the Turkish fishers complain about discards of alien fish
species such as Lagocephalus spp and F. commersonii which have no commercial value in the
Mediterranean part of Turkey.
Some toxic algae give damage to fisheries due to contaminating filter-feeding shellfish species. In
some areas they cause fisheries to be closed or partially closed. Consumption of the contaminated
shellfish can be dangerous for human health.
4.4 Impacts on tourism, human health and other socio-economic activities
Alien jellyfish species are also a threat for tourism. In fact some people had to be hospitalized after
having been in contact with these species in the eastern Mediterranean Sea countries. Jellyfish can be
dangerous in case of allergy. The most important factor is the amount of poison put into blood. Death
rarely occurs, but minor effects can be observed. These can be itching, severe poisoning, muscle
cramps, abdominal rigidity, decrease in touch sensation, nausea, vomiting, serious back pain, speech
difficulties, involuntary muscle contractions and breathing difficulty (Mariottini et al., 2008).
Certainly venomous jellyfish have a negative impact on tourism (Spanier and Galil, 1991). Table 4.3
summarizes the impacts of alien species on tourism and human health either by stinging or by being
eaten. In 2009, several blooms of Rhopilema nomadica were reported and some people were
hospitalized in Antalya, Mersin, Iskenderun and Adana Provinces in the Turkish part of the
Mediterranean Sea (Öztürk and İşinibilir, 2010). R. nomadica is also reported from Greece (Frangou-
Siokou et al., 2006).